Toward a Theory of Island Pedogeography: Testing the driving forces for pedological assemblages in archipelagos of different origins

The Theory of Island Biogeography has been based on biodiversity studies and used as a powerful predictive tool. Currently pedogeography does not have a similar theoretical construct. Although island biodiversity and biological assemblages have been topics of widespread interest in biogeography, ecology and conservation biology, soil scientists have conducted few studies of pedodiversity and pedological assemblages in archipelagos. Several studies have demonstrated that pedodiversity and biodiversity patterns have striking similarities in very disparate environments and at different scales, thus it is possible to test for a similar construct of island pedogeography. We analyze similarities and differences in the pedosphere for three archipelagos with different origins: (i) oceanic-intra-plate chains islands (Hawaiian Islands), (ii) oceanic-intra-plate cluster islands (Canary Islands), (iii) non-marine land-bridge islands with volcanism associated with plate boundary conditions (Aegean Islands) and (iv) as a comparison, islands in a nonplate boundary setting (the British Isles).In the Canary Islands, we also compiled selected biological, physiographical, geological and climatic data for further analysis of pedodiversity, climatic diversity, geodiversity and biodiversity. Our pedogeographic analysis of the three archipelagos indicates archipelagos of varying origins contain different soil assemblages with plate tectonics as the main driving force. The similarities between pedodiversity and biodiversity are more remarkable than the differences.We tested the hypothesis that soil taxa distributions on island chains can be modelled as a power function similar to the species–area relationship (SAR) proposed by McArthur and Wilson for archipelagos. The SAR functional relationship has been widely corroborated in other biodiversity studies. The same patterns were obtained for pedodiversity and biodiversity in the British Isles, and after that in the Aegean Archipelago. In this study we show similar results in the Canary Islands. Furthermore, in the Canary Archipelago, a strong relationship exists between pedodiversity, biodiversity, climate diversity, habitat heterogeneity and relief. For the Hawaii Archipelago, we did not obtain a statistically significant relationship because soil inventories are not published for the smallest islands and islets. However, Hawaii does have a chronosequence from the older to the younger land units. Overall, the dynamics of the underlying plate tectonic hot spots seems to be the major driving force affecting the various diversity types.Based on these results, we suggest a theoretical proposal of “Island pedogeography” consistent and similar to the Theory of Island Biogeography, in view that the latter one also predicts the pedodiversity of soil assemblages in archipelagos. This study illustrates several possibilities for further research in soil geography.